Solar position tracking apparatus comprising a cylindrical light focusing device

ABSTRACT

The present invention relates to an apparatus capable of accurately tracking the movement of the sun. More particularly, the present invention relates to a solar position tracking apparatus comprising: a cylindrical light focusing device; an absorbing device consisting of solar energy absorbing plates; and a device which measures the amount of energy absorbed into each solar energy absorbing plate, and compares the measured amounts.

FIELD OF THE INVENTION

The present invention relates to a solar position tracking apparatus for accurately tracking the position of the sun which is changed every moment due to the rotation of the earth on its own axis, more particularly, a device for accurately and effectively tracking the sun by comprising a cylindrical light focusing device, a solar energy absorbing device and a device for measuring the amount of absorbed solar energy.

The present invention has an object of providing a solar position tracking apparatus and method which always allow the tracking of solar position and also precise tracking thereof.

DESCRIPTION OF RELATED ART

Due to the issues of prevention of global warming and providing environment friendliness, the necessity for solutions of utilizing infinite solar energy as alternative energy is recently highlighted. The solution of utilizing the solar energy includes a technique of directly converting sunlight and solar heat into electrical energy or thermal energy, and for maximally utilizing the solar energy, such a technique requires a solar position tracking apparatus for accurately tracking the solar position by recognizing azimuth and altitude angle of the sun changed every moment in a day, the presence or absence of sunlight etc.

In general, a prior solar position tracking apparatus tracks the solar position with a device constructed so as to give a difference in the amount of energy absorbed by an energy absorbing device such as a plurality of solar sensors, solar cells or photodiodes etc. for absorbing the solar energy. For example, according to Korean Patent No. 10-0836870, the solar position is tracked by measuring and comparing the amount of energy incident on a plurality of solar sensors of the same shape arranged on a bottom of perforated cylinder by means of electrical current generated in the respective sensors. When the sunlight is incident on the solar cell perpendicularly thereto or directly, the value of electrical current is large, and if the tracking apparatus is moved so that the respective solar sensors can have the same value of electrical current, it is decided that the sun is at a position perpendicular to the tracking apparatus. According to Korean Patent No. 10-0904243, the sun is sensed by arranging a partition between light sensors. However, such a method has a problem that if the sunlight is weak as in the morning or evening or the sun is shaded by the cloud etc., the tracking of solar position is impossible because of narrow difference in the amount of energy generated in each energy absorbing device.

Meanwhile, a technique is known of widening the difference by focusing weak sunlight with convex lens, Fresnel lens etc. Korean Patent No. 10-0427690 relates to a cylindrical solar position tracking apparatus with convex lens arranged on its top surface and four photodiodes arranged on its bottom surface, wherein the tracking apparatus is moved in such a way that sunlight focused through the lens can equally shine on the four photodiodes. Korean Patent No. 10-0933661 includes a technique of tracking the solar position by using a lens section utilizing refractive lens and convex lens and photodiodes, wherein values are compared by casting the focal point of sunlight focused through the lens onto the four photodiodes. However, such techniques have problems that it cannot track the solar position until the focal point of lens enters the photodiodes, and it is difficult to accurately align the focal point of lens with the photodiode, and also in the case where while aligning the focal point of lens, the focal point deviates from a surface of the photodiodes due to misalignment or the sunlight appears long after it has disappeared, the position tracking is difficult, and the tracking apparatus has to be always moved along the sun.

Furthermore, in prior art, a separate sensor is attached for grasping the presence or absence of the sunlight.

SUMMARY OF THE PRESENT INVENTION

For solving the above-mentioned problems which the prior solar position tracking techniques have, the present invention provides a solar position tracking apparatus which comprises a cylindrical light focusing device for transmitting, refracting and focusing the sunlight, a solar energy absorbing device arranged on a trajectory of focal point of rear surface of the cylindrical light focusing device and a device for measuring and comparing the amount of energy absorbed by a unit absorbing plate of the absorbing device.

According to the present invention, since the light focusing device is provided, the amount of energy absorbed by an absorbing plate with the sunlight focused thereon and the amount of energy absorbed by a absorbing plate with the sunlight not focused thereon are remarkably different from each other, so the solar position tracking apparatus can be accurately operated even in the case where the sunlight is weak such as in the morning and evening, and by comparing the amount of energy generated in each absorbing plate, the presence or absence of the sun and solar position can be grasped, and the light focusing device does not have mechanically movable parts and enables the solar position to be always tracked.

As described above, according to the present invention, when the sunlight is focused by the cylindrical light focusing device and the focused sunlight is absorbed by the energy absorbing plate, by comparing the amount of energy absorbed by each absorbing plate, the presence or absence of the sunlight and the azimuth and altitude can be easily and accurately grasped.

The cylindrical light focusing device has a advantage that since the focusing device performs its role regardless of incidence angle or altitude angle of the sun. It forms the focal point without needing to be moved. Even in the case where the sunlight is weak as when the sun is shaded by the cloud in the morning and evening, the absorbing plate with focused sunlight absorbed thereby and the absorbing plate with non-focused sunlight absorbed thereby exhibit a great difference in the amount of solar energy, therefore, the solar position can be accurately tracked even without a separate device.

If each absorbing plate shows similar amount of energy or energy ratio, it means the absence of sunlight, while if a difference in the amount of energy is shown, it means the presence of sunlight. Furthermore, if the sunlight appears again long after it has disappeared, a part is present in which the difference in the amount of energy occurs again as mentioned above, and the sunlight is concentrated on the absorbing plate with the greatest amount of energy, therefore, an advantage is obtained that it is possible to always grasp the presence or absence of the sun and position thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view showing a light focusing principle of a cylindrical light focusing device.

FIG. 2 is a perspective view showing an embodiment comprised of a light focusing device and nine solar energy absorbing plates.

FIG. 3 shows a plane view (upper) and front view (lower) of FIG. 2.

FIG. 4 shows a mimetic view of a cylindrical light focusing device and a solar energy absorbing device comprised of a plurality of solar energy absorbing plates and an enlarged sectional view of the energy absorbing device.

FIG. 5 shows a plane view (upper), front view (lower left) and side view (lower right) of the arrangement of the cylindrical light focusing device and a solar energy absorbing device of semi-circular strip shape.

FIG. 6 is a view of sections of the cylindrical light focusing device through which the sunlight passes according to the incidence angle of sunlight.

FIG. 7 is a view showing the change of position of focal point according to the incidence angle of sunlight.

FIG. 8 is a view showing the position of focal point of sunlight which has passed through the cylindrical light focusing device installed on the ground, been refracted thereby and focused and the arrangement of solar energy absorbing plates.

REFERENCE NUMERALS

10: cylindrical light focusing device

11: plate-like energy absorbing device

12: strip-like energy absorbing device

20: sun

21: sunlight beam prior to incidence on a light focusing device

22: sunlight beam refracted inside a light focusing device

23: sunlight beam in the rear of a light focusing device

25: trajectory of movement of sun

30: direction of movement of focal point of sunlight

31: position of focal point

MODE FOR CARRYING OUT THE INVENTION

In the following, referring to the drawings, a detailed description will be given of a solar position tracking apparatus which comprises a cylindrical light focusing device, a solar energy absorbing device and a device for measuring the amount of energy so that the apparatus can conveniently track the solar position without needing to be moved regardless of the position of the sun in a day nor the presence nor the absence of sunlight.

The cylindrical light focusing device (10) of the present invention has a sectional shape of circle, oval or partial circle and is characterized in that it allows identical transmission, refraction and focusing of sunlight regardless of incidence angle of sunlight, therefore, unlike convex lens or Fresnel lens. That is, the cylindrical light focusing device 10 does not have to move to track the sun, and, as shown in FIG. 1, forms a trajectory of focal point at a position distanced from a rear surface of the cylindrical light focusing device 10 by a focal distance thereof depending on the movement of the sun from sunrise to sunset.

As shown in FIG. 2, the solar energy absorbing device comprises a plurality of solar energy absorbing plates 11, each having narrow width and the same plate-like shape, which are continuously circumferentially arranged at the position of the trajectory of focal point of sunlight in a range from angle of sunrise to angle of sunset and each absorb the sunlight.

Projected area of the absorbing plates contacting with the sun is shown in a plane view (upper) in FIG. 3. In the case of the absence of the light focusing device, there is a characteristic that the amount of energy absorbed by respective absorbing plates is related to the projected area of the absorbing plates. On the other hand, as shown in FIG. 4, in the case of the presence of the light focusing device, the absorbing plate receiving the sunlight deviating from the light focusing device exhibits an inherent characteristic value, while the absorbing plates (B, C, D) with the focal point of sunlight formed thereon exhibit a significantly high amount of energy. Next description with reference to an enlarged view of FIG. 4 is about the amount of energy absorbed by the respective absorbing plates. In the case where the focal width of sunlight corresponds approximately to the combined width of two absorbing plates and is included in a range over the absorbing plates (B, C, D), as the amount of energy measured on the respective absorbing plates is proportional to irradiated area, the following relationship is established: absorbing plate (C)>absorbing plate (D)>absorbing plate (B)>absorbing plate (A)≈absorbing plate (E)≈absorbing plate (F). The principle of the present invention will be described by means of the change of the amount of energy of the absorbing plate (B) on which a leading portion of the focal point is present. As the focal point rotates in a rotational direction (30), the area of the absorbing plate (B) receiving the focal point of sunlight is gradually increased and accordingly the amount of energy is gradually increased, and if the leading portion of the focal point has passed the absorbing plate (B), the amount of energy stops being increased, then if a tailing portion of the focal point starts to pass the absorbing plate (B), the amount of energy is gradually decreased, then if the tailing portion of the focal point has completely passed the absorbing plate (B), the amount of energy of the absorbing plate (B) becomes similar to other absorbing plates. That is to say, the amount of energy absorbed by the absorbing plate (B) is changed depending on the position of the sun, and such a phenomenon occurs sequentially in every absorbing plate, and the position of the sun can be recognized by means of comparison of the amount of energy of the respective absorbing plates and the change of the amount of energy of the absorbing plates with the focal point formed thereon.

The width of the solar energy absorbing plate is determined depending on physical properties of the light focusing device such as diameter, refractive property, focal width etc. thereof. For example, in the case where the diameter of the cylindrical light focusing device is 30 cm and the diameter of the trajectory of the focal point is 50 cm, 80 absorbing plates having the width of 0.9 cm can be arranged with a distance of 0.1 cm from each other in the form of semi-circle of about 180 degree on the trajectory of the focal point. One absorbing plate corresponds to about 9 minutes. Several rows of the absorbing plates may be arranged to finely divide the time interval, if necessary.

Each absorbing plate is connected to a device for measuring the amount of absorbed energy and change or change rate of the amount of energy is calculated from the amount of energy of each absorbing plate and the position of sun is determined by comparing the difference in the amount of energy of the absorbing plates. In any case, the sun is present above the opposite side of the light focusing device with respect to the absorbing plates exhibiting the highest amount of energy. The device for measuring the amount of energy is a device for measuring the amount of solar energy absorbed by the respective solar energy absorbing plates as the amount of electrical energy or thermal energy. If solar cells are used for the absorbing plates, the solar energy is absorbed by the respective absorbing plates and electrical current or power as electrical energy is generated in the absorbing plates, and the device for measuring the amount of energy is a device for measuring the amount of electrical energy by measuring the electrical current or power generated in the absorbing plates. In the case where a device such as metal plate absorbing thermal energy is used for the absorbing plates, the solar energy is absorbed by the respective absorbing plates, whereby the temperature of the absorbing plates is changed, and the device for measuring the amount of energy is a device for measuring the amount of thermal energy by measuring the temperature of the absorbing plates.

FIG. 5 is a view of a solar position tracking apparatus that comprises a solar energy absorbing device consisting of six solar energy absorbing plates (12) of semi-circular strip shape successively arranged in an axial direction in the vicinity of the trajectory of focal point of the rear surface of the cylindrical light focusing device and a device for measuring the amount of energy. Each absorbing plate has a different diameter, but has the same center as that of the light focusing device. Distance of each absorbing plate from the center of the light focusing device is made slightly different from another absorbing plate for obtaining difference in the degree of concentration of sunlight. Each absorbing plate is connected to the device for measuring the amount of energy, thus the degree of absorption of sunlight can be grasped.

FIG. 6 shows several sections taken according to the angle of sunlight incident on the cylindrical light focusing device, and the focal distance of sunlight passing along these sections are different. The focal distance (31) of sunlight from the center of the light focusing device is longest for a normal incidence as seen in FIG. 4.

FIG. 8 is a view showing how the solar position tracking apparatus of the present invention installed in the ground operates in the morning/afternoon and at noon, wherein since the altitude of the sun is low in the morning and afternoon, the sunlight obliquely passing through the light focusing device forms the focal point on the absorbing plate (K). For the amount of energy absorbed by the respective absorbing plates in the morning, the following relationship is established: absorbing plate (K)>absorbing plate (J)>absorbing plate (L)>absorbing plate (M)>absorbing plate (N). With the passage of time, the incidence angle of sunlight gradually become larger over time and the focal length becomes longer, so the focal point is formed on the absorbing plate (M) at noon and the largest amount of energy is measured on this absorbing plate. At noon, the following relationship is established: absorbing plate (M)>absorbing plate (L)>absorbing plate (N)>absorbing plate (K)>absorbing plate (J). In the afternoon, an opposite relationship is established again. By comparison of the amount of energy and ratio thereof of each absorbing plate, the incidence angle of sunlight can be grasped, whereby the position of the sun can be accurately tracked. 

What is claimed:
 1. A solar position tracking apparatus comprising: a cylindrical light focusing device which is in the form of longitudinally (axially) elongate solid rod (cylinder) and transmits, refracts and focuses sunlight incident from a front surface of the device to form focal point at a position distanced from a rear surface of the rod by a focal distance; a solar energy absorbing device comprising a plurality of solar energy absorbing plates, each plate having a width smaller than a physical diameter of the cylindrical light focusing device, the plurality of solar energy absorbing plates having the same size and shape and being successively arranged around the focusing device at a trajectory of focal points formed in a rear face of the cylindrical light focusing device depending on the movement of sun, the absorbing device being coaxial with the focusing device; and a device for measuring the amount of energy absorbed by the respective solar energy absorbing plates.
 2. A solar position tracking apparatus comprising: a cylindrical light focusing device which is in the form of longitudinally (axially) elongate solid rod (cylinder) and transmits, refracts and focuses sunlight incident from a front surface of the device to form focal point at a position distanced from a rear surface of the rod by a focal distance; a solar energy absorbing device comprising a plurality of solar energy absorbing plates, each plate having a semi-circular strip shape, the plurality of solar energy absorbing plates having different radii and being successively arranged in a radius direction, each plate extending in a longitudinal direction of the cylindrical light focusing device in the vicinity of a position of focal point formed in a rear face of the cylindrical light focusing device, and each semi-circular plate of the absorbing device being coaxial with the focusing device; and a device for measuring the amount of energy absorbed by the respective solar energy absorbing plates.
 3. The solar position tracking apparatus according to claim 1 or 2, wherein the cylindrical light focusing device comprises a light focusing device which forms the focal point on an opposite side with respect to an incidence direction of the sunlight and has a section of circular or oval or partially circular shape.
 4. The solar position tracking apparatus according to claim 1 or 2, wherein the cylindrical light focusing device comprises a pipe-type light focusing device which by can adjust the temperature of the solar energy absorbing plates by allowing liquid such as water to flow inside the device to absorb a portion of the sunlight.
 5. The solar position tracking apparatus according to claim 1 or 2, wherein the cylindrical light focusing device comprises a light focusing device of which the inside and outside consist of material having different refractive index so as to adjust a focal length.
 6. The solar position tracking apparatus according to claim 1 or 2, wherein the solar energy absorbing device is comprised of solar cells and the device for measuring the amount of energy comprises a device for measuring the amount of electrical energy generated from the solar cells.
 7. The solar position tracking apparatus according to claim 1 or 2, wherein the device for measuring the amount of energy comprises a device for measuring thermal energy absorbed by the solar energy absorbing device. 